Heat transfer apparatus



April 16, 1963 E. BOGNAR ET AL 3,035,626

HEAT TRANSFER APPARATUS Filed March 20, 1956 ZB r /8 /3 1 & =4

, /5 T INVENTORS. 12m 5W BY W Mm 7mm 5mm J ATTORN Y5 United StatesPatent 3,085,626 HEAT TRANSFER APPARATUS Etienne Bognar and MichelAntoine Maistre, Paris, France, assignors to Compagnie de Saint-Gobain,Paris,

France Filed Mar. 20, 1956, Ser. No. 572,714 Claims priority,application France Mar. 21, 1955 1 Claim. (Cl. 16511) This inventionrelates to heat exchange apparatus for transferring heat energy from onefluid to another and more particularly for making efficient, practicaluse of heat energy, such as that released by exothermic reactions athigh temperatures.

It is known that calories or heat energy released by certain exothermicreactions may be utilized to vaporize substances, such as mercury,having high boiling points thereby storing the heat energy in the vapor.The latter may then be employed as a source of heat in a heat exchangerwherein the vapor is condensed and the heat energy converted to a usefulpurpose such as the heating of water to produce steam under pressure. Inpractice difficulties have been encountered in constructing suitableheat exchange apparatus in which the high temperature condensable vaporand the water to be converted to steam are in contact with oppositesurfaces of the same wall. In such constructions, the walls are subjectto deformation by reasons of differences in term peratures, difienencesin the vapor tensions of the two fluids and the like, thus causingruptures and creating leaks which permit penetration of one fluid intothe circuit of the other, a condition which cannot be tolerated.Heretofore, efforts have been made to avod this latter difliculty byproviding bulky apparatus which are expensive to build and requireconsiderable space for installation. In some prior known equipment aninert intermediate fluid has been employed as the caloric vehiclebetween the heated vapor and the fluid to be heated, but the operationof such equipment has been found to be inefficient because ofunavoidable heat losses entailed in the multiple exchange-s necessaryand hence expensive to operate.

Accordingly, it is one of the objects of the present invention toprovide a novel apparatus whereby the toregoing difiiculties anddisadvantages of prior known devices are overcome.

Another object of the invention is to provide a novel recuperativeboiler or heat exchange apparatus whereby the vapors of a liquid underpressure, such as water, is efiected directly by utilizing the heat ofcondensation of a fluid at high temperature and under comparatively lowpressure. p

A further object is to provide novel heat exchange apparatus of theabove type'which is capable of functioning with high efiiciency.

Still another object is to provide a heat exchanger which is novelly soconstructed as to effectively eliminate the danger .of any mixing of theheat releasing and heat absorbing fluids in the event of a rupture inthe apparatus and to facilitate inspection servicing and repair.

A still further object is to provide a simply constructed heat exchangeapparatus wherein the transfer of heat takes place by both convectionand radiation, principally the latter in an elficient manner.

The above and further objects and novel features of the presentinvention will more fully appear from the following detail descriptionwhen the same is read in connection with the accompanying drawings. Itis to be expressly understood, however, that the drawngs are for thepurpose of illustration only and are not intended as a definition of thelimits of the invention.

The single FIGURE of the drawing is a schematic, vertical sectional viewillustrating the construction of one form of heat exchange apparatusembodying the invention.

The single embodiment of the invention illustrated in the drawing, byway of example, comprises two principal separable sections, the uppersection B being herein referred to as the boiler section, and the lowersection C being called the condenser section. In the form shown, boilersection B, which contains Water and steam or other fluid to be heated,comprises a casing 1 having a perforated bottom plate 7, a removablecover 3 for a manhole, and the customary accessories such as a pressuregauge 5 and a water level indicator 4. Water is fed into section Bthrough a conduit 20* under control of a suitable valve 21 and steam isreleased through a conduit 2 under control of a suitable valve 22.

Secured within each of the perforations in plate 7 in a gas-tight mannerand extending downwardly therefrom is a tube 6. Each such tube is closedat its lower end and opens into casing 1 at its upper end. Within eachtube is a downflow pipe or conduit 23 which is preferably centrallydisposed in said tube and terminates short of the bottom or closed endof the latter. Pipes 23 may be sup ported by plate 7 or tubes 6 in anysuitable known manner such as by one or more spiders (not shown) and thesame preferably extend above plate 7 into the boiler chamber. When thedevice is operating, the heated Water in the 'outer annular passage ofeach tube system 6, 23 rises and cooler water descends through centralconduit 26 to replace it as indicated by arrows.

The condenser'section C, in the form illustrated, comprises acylindrical casing member 8 having an upper p ate 9 and a lower plate10, said plates having aligned perforations. Sections B and C are spacedapart by 'a ring 12 and may be sepa ablyv secured together by anysuitable known means such as clamps, bolts or the like (not shown). Thespace within casing 8 is divided or partitioned by a plurality of tubesor cylinders 11, one of the latter surrounding each of the double wallwater pipes 6, 23. The ends of cylinders 11 fit into the perforations oropenings in plates 9 and 10 and are securely fastened to said plates ina gas tight manner.

" annular chamber or space 16 which is in communication through openings17 with the annular spaces 18 in cylinders 11' around tube 6 and, hence,with the space between plates 7 and 9. The conduit 15 serves both as aninlet for high temperature vapors to the space 14 surroundingcylindrical partitions 11 and as an outlet for the condensate from suchvapors.

It will thus be seen that the annular spaces 18 between walls 11 andtubes 6 are interconnected at their upper ends by the space betweenplates 7 and 9, and are interconnected at their lower ends by conicalannular chamber 16. To facilitate the transfer of heat energy from walls11 to the walls of tubes 6, the adjacent surfaces thereof, i.e., thesurfaces within space :18 are delustered or coated with a suitable agentor treated in any other known manner so as to render the heat radiationfactor thereof as high as possible. As will hereinafter more fullyappear, the exchange of heat between walls 11 and 6 is effected byconvection currents of a gaseous medium, such as air, enclosed in theintermediate spaces 18 and by radiation. The transmission by radiationcan be of particular importance in view of the comparatively hightemperatures which may be involved. The quantity of heat transmitted bythe radiation is, in fact, proportional to the diflerence between the4th powers of the absolute temperatures of the walls 11 and 6.

In the event of any internal leakage of steam, water or other fluid fromthe boiler section or of the mercury, vapor or similar fluid from thecondenser section, such leakage will take place into the intermediatespace 18 and will accumulate in chamber 16 from .which the same may bedrained through a valve 19. The pressure within space 16, 18 may also becarefully regulated through valve 19 or in any other desired manner. Inthe event of any serious rupture which results in any considerableleakage from one of the fluid circuits into space 16, 18, the same maybe readily located and repaired by separating the boiler and thecondenser sections at ring 12.

In the operation of the above described apparatus, a vapor at hightemperature, such as mercury vapor, is created in any suitable knowntype of device by the utilization of heat energy from any suitablesource, such as the heat generated by an exothermic reaction, and isconducted through a pipe 15 into condenser chamber 14 around cylinders11. The boiler section including tubes 6, 23 is filled to a suitablelevel with Water or with other fluid to be heated. Upon contact withcylindrical walls 11, the mercury vapor condenses and the condensatedrains out through pipe 15. The heat energy released by the condensationof the vapor is transmitted chiefly by radiation from walls 11 throughspace 18 to the walls of tubes 6 and, thence, to the water or otherfluid therein. To a lesser degree some of such heat energy istransferred by convection in the currents of the gaseous medium, whichmay be air, in the spaces 18.

In some successful apparatus built and operated in accordance with theinvention herein described, it has been possible to recuperatesubstantially all of the heat energy from mercury vapor at an absolutepressure of 3.5 kg. and a temperature of 430 C., with an average inputof about 10,000 kg. of mercury per hour. Using a heat exchanging surfaceof 90 square meters 1000 kg. of steam have been generated under apressure of 12 kg. Under the same conditions, .but with an exchangesurface of 96 square meters, 950 kg. of steam have been generated at apressure of 20 kg. With the same input of mercury at 8 kg. absolutepressure and a temperature of 500 C. the energy of the heat ofcondensation has been substantially fully recovered in a boilerconstructed in accordance with the invention and having a heat exchangesurface of 56 square meters and generating 1000 kg. of steam at apressure of 12 kg.

There is thus provided a practical and elficient heat exchange apparatusadapted for use in converting the heat of condensation of the vapors ofliquids having comparatively high vaporization temperatures.Additionally, said apparatus is of simplified construction and smallsize in comparison with prior apparatus of comparable capacity and yet,even more reliable in operation. The apparatus of the invention is alsocomparably inexpensive to manufacture, install and operate.

Although only a single embodiment of the invention is illustrated in theaccompanying drawing and described in detail in the foregoingspecification, it is to be specifically understood that the invention isnot limited thereto, but that various changes may be made in the detailsof construction and in the design and arrangement of the partsillustrated without departing from the spirit and scope of theinvention.

What is claimed is:

A boiler, adapted to be partially filled with a liquid to be vaporized,heated by the condensation heat of a substance such as mercury vaporizedin recuperating the heat released by exothermic reaction, said boilerincluding an inlet below and an outlet above the liquid level in aclosed upper boiler section comprising a casing having a bottom wall, aplurality of parallel tubes sealed to and projecting verticallydownwardly from said bottom wall and communicating with the interior ofsaid casing, the lower ends of said tubes being closed, and a pipeextending into each of said tubes from said casing and terminating shortof the closed lower end of the tube, the closed space within the boilersection being made up of the space within the casing and the spaceswithin the tubes communicating therewith, and a closed lower condensersection having an upper wall, said tubes of the boiler section extendingthrough openings in the said upper wall of the condenser into theinterior thereof, partition means extending a substantial distancewithin said condenser casing, said partition means having their upperends sealed to said upper wall and creating in the condenser chamber avapor chamber and annular gas containing spaces around said tubes sealedfrom said vapor chamber and from the interior of said tubes and from theinterior of the tubes of the boiler section, means removably securingthe lower wall of the boiler and the upper wall of the condensertogether in confronting relationship, the condenser section having acommon header space adjacent the bottom thereof connecting the lowerends of said annular spaces, and means selectively to open the bottom ofthe header space and to close said header space, whereby to detect anddrain any leakage of fluid from either the boiler section or thecondenser section into any of said annular spaces.

References Cited in the file of this patent UNITED STATES PATENTS710,608 Prat Oct. 7, 1902 1,419,337 Werner June 13, 1922 1,628,736Oliver May 17, 1927 1,761,035 Govers June 3, 1930 2,225,634 Houdry Dec.24, 1940 2,658,728 Evans Nov. 10, 1953 2,669,435 Cord et al. Feb. 16,1954 FOREIGN PATENTS 588,214 Great Britain May 16, 1947

